I've been tooling around with building a desktop power supply for some time now. It started out as just a simple modified AT power supply, which gave me +12, +5, -5 and -12 VDC. I added a piece of plexi with a selector switch, volt and amp meters, a 30 amp circuit breaker and both output lugs and 5 way binding posts. This worked well enough till I needed more than the available 5 amps.
The next iteration was the addition of a second transformer and another selector switch. The transformer is a microwave oven transformer from McDonalds, with the the secondary winding removed and rewound with 12 gauge sold wire (a single strand from romex). I get 24 VAC unloaded with an optional center tap(not used at this time). I then added a 40 amp bridge rectifier and a large cap to give a simple, high current DC power supply. This works well enough. It holds 30 volts with up to a 8 amp load, then starts dropping from there and ends up at 24v at 30 amps. Don't think that's too bad for having next to no idea what I'm doing. It works well enough, but time has come to make a a more reliable voltage source for high current devices. With out any regulation, I've fried a handful of projects, so this got pushed up on my list of priorities.
The AT power supply side is going to stay as it is, but I want to add voltage regulation and *maybe* current regulation. What I was thinking about building is something like a buck dc-dc power supply. Using a LM317 as an adjustable reference voltage, I want to use an opamp to switch a set of mosfets. On the output, I am planning on using a capacitor directly fed from the mosfets and an inductor to filter the output. Anyone have a diagram for something like this? I've been poking around here and on google, but have had no luck. Also, any ideas for adding current regulation?
The next iteration was the addition of a second transformer and another selector switch. The transformer is a microwave oven transformer from McDonalds, with the the secondary winding removed and rewound with 12 gauge sold wire (a single strand from romex). I get 24 VAC unloaded with an optional center tap(not used at this time). I then added a 40 amp bridge rectifier and a large cap to give a simple, high current DC power supply. This works well enough. It holds 30 volts with up to a 8 amp load, then starts dropping from there and ends up at 24v at 30 amps. Don't think that's too bad for having next to no idea what I'm doing. It works well enough, but time has come to make a a more reliable voltage source for high current devices. With out any regulation, I've fried a handful of projects, so this got pushed up on my list of priorities.
The AT power supply side is going to stay as it is, but I want to add voltage regulation and *maybe* current regulation. What I was thinking about building is something like a buck dc-dc power supply. Using a LM317 as an adjustable reference voltage, I want to use an opamp to switch a set of mosfets. On the output, I am planning on using a capacitor directly fed from the mosfets and an inductor to filter the output. Anyone have a diagram for something like this? I've been poking around here and on google, but have had no luck. Also, any ideas for adding current regulation?
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